He was treated at a Denbighshire hospital in 2010 but the sisters said they have not been able to view the inquiry into his care.

Betsi Cadwaladr University Health Board said its inquiries were continuing.

We still haven't got justice for our mum, and what's really important for us now as a family is an independent reviewSarah Mills-Westley

Deyanov was sectioned under the Mental Health Act and detained at Glan Clwyd Hospital in summer 2010, but travelled to the Spanish island after he was released that October.

He murdered Mrs Mills-Westley, 60, in May 2011 while she was shopping in the resort of Los Christianos.

Deyanov, a drifter who believed he was Jesus Christ and heard voices commanding him to kill, had been living rough and taking drugs in a derelict building on a nearby beach.

After a series of random violent attacks in January 2011, he was committed to a Tenerife psychiatric unit but released on bail the following month. Days before the killing a warrant was issued for his arrest.

Image caption
Jennifer Mills-Westley had retired to the island of Tenerife

After his conviction and sentence to 20 years in a secure psychiatric unit, Samantha Mills-Westley, 39, and her sister Sarah, 43, criticised the authorities in north Wales for their handling of Deyanov and demanded an independent review.

The sisters met Deyanov's aunt in north Wales to ask if he had received the right care.

...we can state categorically that the decision to discharge Mr Deyanov was in no way influenced by issues of funding or shortages of bedsBetsi Cadwaladr University Health Board

Samantha Mills-Westley told the Channel 4 programme Dispatches: "When he first got admitted, he was relatively well-behaved, even though he was showing signs of having schizophrenic episodes, of talking to people who didn't exist. Telling his aunty that he was God.

"The second time he was admitted, she said that his behaviour had really become incredibly erratic. That he was becoming violent."

Her sister added:"It appears that Deyanov left the hospital without a treatment plan and that the family had no idea that a) he had been released or that b) there was a mechanism of support that should have been released with him.

"It was really up to him to sort himself out.

"We still haven't got justice for our mum, and what's really important for us now as a family is an independent review."

The sisters said they know that the health board conducted an inquiry into Deyanov's care but they have been refused access to it.